\section{Motivation}
The use of mobile devices has changed the way people relates with information. Nowadays it is possible to access, visualize and modify data from remote locations in the same way as we do in a big metropolis. This way, the possibilities for using information technologies in field work has become a reality. For an amateur astronomer the best sites for observation are usually away from urban areas, where it is possible to avoid artificial lights and other sources of light pollution. 

We developed StarGazer considering the following scenario in mind: There is an amateur astronomer doing field work away from the city. She is searching for certain stars in the sky, however, she forgot to bring her star charts that helps her to find the stars she is looking for. Based on this, mobile technologies are the only way to communicate and obtain information that she didn't bring with her. 
Is in this scenario where StarGazer can help to improve the experience for amateur astronomers where they are able to access information about stars, their composition, position, etc. using the Web as the source of information. Moreover StarGazer allows the user to share the information she has obtained from her observation point with other users: This way it is possible for other amateur astronomers to go to the same. Based on this situation, we present the following use cases.
\subsection{Objectives}
More specifically we are looking to develop an application that complies with certain goals and objectives.
\begin{itemize}
\item {\bf Web-based:} Our application must be Web-based in order to be able to work with different devices, ranging from desktop computers to mobile cellphones. Moreover, StarGazer must be based on standards to allow all these devices to access the information provided.
\item {\bf Interoperable:} Since we are not necessarily expecting that the user will be human, we should encourage the interoperability of StarGazer with other web-based systems or applications. In this sense, it will be possible to use the information provided by our application in other ways we haven't thought of. To accomplish this objective, we used OWL as the language to express the knowledge.
\item {\bf Easy to extend:} We were concerned that StarGazer can be extended to include other functionalities and knowledge we haven't implemented yet. In order to allow that, we have developed it using software packages that encourages the use of best practices. Also, we have left some ``hooks'' in our ontology, ready to extend it with knowledge about other celestial bodies.
\end{itemize}
\subsection{Use cases}
We developed StarGazer based on several use cases: All of them are related to the idea of having a user only connected to Internet from her mobile device, that allows her to use StarGazer.
\subsubsection{Case 1}
{\bf Name:} FindStarByMagnitude\\
{\bf Goal:} Select all the stars from certain area of the sky and show their name, apparent magnitude, distance and spectral type ordered descending by apparent magnitude.\\
{\bf Summary:} The user queries the system for certain area (given by a range of right ascension and 
declination). The system looks for all the stars in the database backend that are in this 
range sorts them and it returns their names, apparent magnitude, distance and spectral type 
ordered by apparent magnitude from brighter to dimmer. 
\subsubsection{Case 2}
{\bf Name:} ExportLocation\\
{\bf Goal:} Export (and publish) a geolocation.\\
{\bf Summary:} The user marks the current location for exporting it for future uses or sharing with other users in RDF format.
\subsubsection{Case 3}
{\bf Name:} ShowRelatedInformation\\
{\bf Goal:} Obtain the information related to certain star.\\
{\bf Summary:} The user selects a star and the system shows all the objects related to that type.